Physical quantity sensor and method for manufacturing the same

Abstract

A physical quantity sensor includes two substrates and a movable electrode that is disposed between the two substrates and is bonded to the two substrates. In the physical quantity sensor, the movable electrode has an elastically deformable diaphragm and one of the two substrates is an electrode substrate having a detection electrode on a detection surface opposite to the diaphragm to detect capacitance between the diaphragm and the detection electrode. In the physical quantity sensor, in a range between a room temperature and a bonding temperature when the two substrates and the movable electrode are bonded, coefficients of thermal expansion of the two substrates are smaller than that of the movable electrode and in a temperature range where the physical quantity sensor is used, a coefficient of thermal expansion of the movable electrode is between a first and second substrates.

1. A physical quantity sensor, comprising:
 two substrates; and 
 a movable electrode that is disposed between the two substrates and is bonded to the two substrates, wherein 
 the movable electrode is provided with an elastically deformable diaphragm, 
 at least one of the two substrates is an electrode substrate having one or more detection electrodes on a surface opposite to the diaphragm to detect a change in capacitance between the diaphragm and the detection electrode, and wherein, 
 in a range between a room temperature and a bonding temperature when the two substrates are bonded to the movable electrode, coefficients of thermal expansion of the two substrates are smaller than a coefficient of thermal expansion of the movable electrode, and, 
 the two substrates are a first substrate and a second substrate having different coefficients of thermal expansion with each other in a temperature range where the physical quantity sensor is used, the coefficient of thermal expansion of the movable electrode being between the coefficients of thermal expansion of the first substrate and the second substrate in a temperature range where the physical quantity sensor is used. 
 
     
     
       2. The physical quantity sensor according to  claim 1 , wherein
 the movable electrode is provided with two recesses, each of the two recesses being provided on surfaces opposing the two substrates, and 
 the diaphragm is a thin portion located between bottom surfaces of the two recesses, wherein 
 one of the two recesses is deeper than the other of the two recesses, and 
 the bottom surface of the one of the two recesses is larger in area than that of the other of the two recesses. 
 
     
     
       3. A method for manufacturing the physical quantity sensor according to  claim 2 , further comprising:
 anodically bonding the electrode substrates and the movable electrode while the electrical potentials of the detection electrode formed on the electrode substrates and the movable electrode are equalized. 
 
     
     
       4. The method for manufacturing the physical quantity sensor according to  claim 3 , wherein
 the bonding comprising 
 laminating a substrate wafer in which a plurality of the substrates are integrally formed, and a diaphragm wafer in which a plurality of the movable substrates are integrally formed; 
 applying voltage to a bonding electrode that is formed on the substrate wafer in a predetermined pattern to anodically bond the substrate wafer and the diaphragm wafer with each other; and 
 cutting the substrate wafer and the diaphragm wafer anodically bonded in the voltage-applying along a cutting line, wherein 
 at least a part of the bonding electrode is provided along the cutting line. 
 
     
     
       5. A method for manufacturing the physical quantity sensor according to  claim 1 , comprising:
 anodically bonding the electrode substrate and the movable electrode while the electrical potentials of the detection electrode formed on the electrode substrate and the movable electrode are equalized. 
 
     
     
       6. The method for manufacturing the physical quantity sensor according to  claim 5 , wherein
 the bonding comprising: 
 laminating a substrate wafer in which a plurality of the substrates are integrally formed, and a diaphragm wafer in which a plurality of the movable electrodes are integrally formed; 
 applying voltage to a bonding electrode that is formed on the substrate wafer in a predetermined pattern to anodically bond the substrate wafer and the diaphragm wafer with each other; and 
 cutting the substrate wafer and the diaphragm wafer anodically bonded in the voltage-applying along a cutting line, wherein 
 at least a part of the bonding electrode is provided along the cutting line.